The present invention relates to an inhaler device for dispensing medicament by inhalation. In particular the invention relates to a multiple-dose dry powder inhaler having a dose counter for indicating the number of metered doses of medicament that have been dispensed from, or remain in, the medicament container of the inhaler device.
The administering of a powdered drug preparation by inhalation from an inhaler device is known. Typical inhalation devices include pressurized metered dose inhalers (pMDI) having a canister with particulate medicament suspended in propellant gas and dry powder inhalers (DPI) having a container of powdered medicament without propellant gas.
Various dose counters have been described which are intended for use in pressurized metered dose inhalers or dry powder inhalers. The dose counters generally help the patient to keep track of the number of doses still available from the inhaler device and thereby warn the patient when the inhaler nears exhaustion. The dose counters usually have in common the feature that they detect the relative movement between the medicament container and the actuating or dosing member, and increment in response to such movement
For example, International patent publication WO 86/05991 describes a multiple-dose powder inhaler having a dose counter comprising a counting wheel vertically mounted above a horizontally mounted perforated dosing disc said counting wheel being rotated by a worn drive forming part of the rotatable dosing disc.
International patent publication WO 97/20589 describes a multiple-dose powder inhaler with a dose counter comprising a co-axially mounted set of units wheel, tens wheel and hundreds wheel, wherein the units wheel is driven by a spring leaf connected to a longitudinally movable dosing slide.
International patent publication WO 92/00771 describes a multiple-dose powder inhaler having a rotatable dosing member and a dose counter comprising a tape secured to the axle of the metering member the tape being wound onto said axle upon rotation of the metering member. In another embodiment the dose counter comprises a counting ring and a driving disc arranged co-axially with the metering member the driving disc being equipped with a spring arm. When the driving disc completes one rotation, the spring arm cooperates with a cam secured to the housing and engages with the counting disc.
U.S. Pat. No. 5,687,710 describes a multiple-dose powder inhaler having a rotatable dosing plate and a dose counter comprising a continuous and intermittent counter rings. The counter rings are co-axially mounted and have counting indicia on their outer surfaces. An actuating means has a pawl for engaging with the gear teeth of the continuous and intermittent counter rings.
European patent publication EP 488609 describes a multiple-dose powder inhaler having a longitudinally movable dosing member and a dose counter comprising an actuating finger for rotating an indexing gear. The indexing gear is connected via a worm drive to a gear wheel equipped with counting indicia.
International patent publication WO 94/11044 describes a multiple-dose powder inhaler having a rotatable dosing member and a dose counter comprising a ratchet wheel cooperating with the actuating means, an eccentric orbital gear and a cover plate having counting indicia thereon.
The above constructions have a drawback that they are bulky or have complex moving parts which can be difficult to assemble and expensive to manufacture.
A multiple-dose dry powder inhaler sold under the trademark Easyhaler comprises a counter wheel having gear teeth and counting indicia the counter wheel being driven by a pin extending from a rotatable metering member. The counter wheel is rotatably mounted on two arcuate bearing ribs, which match a circular groove formed near the periphery of the counter wheel. Whilst the construction is simple and compact, it has a drawback that the counter wheel is susceptible to unintentional movements or jamming, as the bearing ribs have a double function of bearing and braking the counter wheel.
There is need for a powder inhaler having a dose counter which avoids the above disadvantages. In particular, the counter unit should comprise a relatively few, simple mechanical parts, should not require excessive amounts of space and should provide at the same time reliable counting function.
The present invention provides a multiple-dose powder inhaler for dispensing powdered medicament by inhalation comprising
an inhaler body defining a medicament container for receiving a plurality of powdered medicament doses;
an air channel through which air is drawn via a mouthpiece;
a metering drum rotatable about its rotational axis and having one or more peripheral dosing recesses for receiving in one position a metered dose of the powdered medicament from the medicament container and for bringing in another position the metered dose of the powdered medicament to the air channel; and
a dose counter for indicating the number of metered doses of medicament that have been dispensed from, or remain in, the medicament container, said dose counter comprising
a counter wheel having a central hole said counter wheel being rotatably mounted about a bearing axle having a longitudinal axis substantially parallel to and spaced from the rotational axis of the metering drum, said bearing axle extending from the inhaler body and though the central hole, and said counter wheel having counting indicia thereon and a plurality of gear teeth;
extending from the metering drum a driving pin adapted to engage with at least one of said plurality of gear teeth of the counter wheel upon every complete revolution of the metering drum so as to rotate said counter wheel an incremental amount; and
a flexible brake finger extending from the inhaler body and adapted to engage with the counter wheel so as to maintain a unidirectional rotation and to prevent unintentional movement of the counter wheel.
The dose counter of the present invention detects the stepwise rotation of the metering drum between a loading position, wherein the dosing recess of the metering drum is loaded with a dose of medicament, and the inhalation position, wherein the filled dosing recess is brought to the air channel. Preferably the stepwise rotation of the metering drum is achieved by means of a ratchet wheel. The ratchet wheel is suitably co-axial and integrated with the metering drum into a one-piece component.
The ratchet wheel of the metering drum can be manually operated. Preferably the ratchet wheel of the metering drum is driven by a longitudinally movable actuating member. For example, the inhaler can be actuated by means of an axial movement of a depressible cover. In such embodiment the depressible cover may comprise an elongate pawl adapted to engage with the ratchet wheel of the metering drum upon each axial movement of the cover. A complete revolution of the metering drum is then accomplished by making a predetermined number of said axial movements of the cover, such number being dependent on the number of teeth in the ratchet wheel.
The counter wheel is provided with a plurality of gear teeth and comprises preferably a relatively flat top portion having counting indicia, typically alpha-numerical characters, placed thereon. The gear teeth can be configured in the counter wheel in a suitable way such as to the outer periphery. In a preferred embodiment the counting wheel comprises a circumferential skirt portion and the gear teeth are formed around the inner circumference of the skirt such that the gear teeth are facing inwardly towards the axis of the counter wheel.
The counter wheel is rotatably mounted on a bearing axle extending from the inhaler body. In a preferred embodiment the bearing axle extends from the outer wall of the medicament container. The counter wheel has a central hole through which the bearing axle extends, such that the counter wheel is supported by the bearing axle. The counter wheel is disposed adjacent to the metering drum in such a way that the rotational axis of the counter wheel is substantially parallel to but spaced from the rotational axis of the metering drum.
The counter wheel is driven by a pin extending from the flat surface of the metering drum in the direction of the counter wheel. The portion of the pin engaging with the gear teeth of the counter wheel is generally set off from the axis of the metering drum such that the engagement occurs only upon every complete revolution of the metering drum. The pin can also be configured as a gear wheel extending co-axially with the metering drum, wherein all other teeth of the gear wheel except one are cut away. In such embodiment the one remaining tooth of the gear wheel acts as the driving pin. In operation, the driving pin is adapted to engage with at least one of the gear teeth of the counter wheel upon every complete revolution of the metering drum so as to rotate said counter wheel an incremental amount. Said incremental amount is generally depending on the number of teeth in the counter wheel. The predetermined number of axial movements of the depressible cover required to cause the counter wheel to rotate a complete revolution depends on the number of teeth in the ratchet wheel and the counter wheel. Typically it is intended that the counter wheel makes only one single revolution during the lifetime of the inhaler.
Preferably the inwardly facing teeth are formed around only a portion of the inner circumference of the skirt of the counter wheel such that a gap is formed therebetween. This ensures that the counter wheel cannot be advanced past the last indicia indicating that the container is empty.
The flexible brake finger extending from the inhaler body is preferably adapted to engage with at least one of said plurality of gear teeth of the counter wheel. In a preferred embodiment of the invention the flexible brake finger is adapted to engage simultaneously with the engagement portion of at least two non-adjacent gear teeth of the counter wheel. This ensures that the counter wheel is not susceptible to unintentional movements, and in particular that the counter wheel is steady also in such position where the brake finger encounters said gap between the teeth of the counter wheel.
It is also possible to configure the flexible brake finger such that it engages with additional gear wheel, which is disposed e.g. on the outer periphery of the counter wheel. In such embodiment the counter wheel is provided with two gear wheels, one for the incremental rotation by the driving pin and one for the engagement by the brake finger.
Preferably the flexible brake finger is configured as having two curved surfaces, for the engagement simultaneously with a engagement surface of at least two non-adjacent gear teeth, and a bridge connecting said curved surfaces.